Graving dock



Sept. 25, 1951 E. T. LARsEN YGRAVING DOCK e Sheets-Sheet 1 Filed Nov.22, 1946 lNl/EN TOR E/NAR 7T LARSE/V 8K WY 1 Sept. 25, 1951 E. 1 LARSEN2,568,751

' GRAVING DOCK 6 Sheet-Sheet 2 Filed Nov. ,22, 1946 INVENTOR E/NAR 7.QARSEN B) W Y Sept. 25, 1951 Filed Nov. 22, 1946 E. T. LARSEN 2,568,751

GRAVING DOCK 6 Sheets-Sheet 5 INVENTOR E/NAR 7: LARSEN Sept. 25, 195i E.T. LARSEN GRAVING DOCK v 6 Sheets-Sheet 4 Filed Nov. 22. 1946 J lzvvclvran ff/VAR r LARSEIY I I I 6 Sept. 25, 1951 E. T. LARSEN GRAVING DOCK 6Sheets-Sheet 5 IN l/ENTOR EINAR 7'. LARSEN er W E. T. LARSEN GRAVINGDOCK Sept. 25, 1951 6 Sheets-Sheet 6 Filed Nov. 22, 1946 INVENTOR E/NAR1t LARSEN llllll Ill Patented Sept. 25, 1951 UNITED STAT E S PAT ENTOFFI CE 2,568,751 GRAviNG DOCK Einar T. Larsen, akland,-.,balii.,, assignor to Kaiser Steel Corporation Application November 22, 194d, SerialN6. 711;741

11 Claims.

This invention relates to gates for graving docks'which afford a drybasin, in' which ships can be repaired or otherwise serviced and newships canibebuilt.

Such docks are conventionally located with the gate at the sea or otherbody of water in which: the ships can be floated which are to beserviced, repaired or built in the docks. The function of the gate whenclosed is to seal ofi the basin from such water so that the basin can bepumped dry to permit repair or other service, or construction of a shiptherein, without substantial leakage of such water thereinto. The gateis opened-so that a ship to be repaired can be floated into the basin ora serviced or newly built-ship can be floated out of it. It has beenconsidered necessary that graving dock gates be large and heavy w herelarge-ships are to be accommodated, v'v'ith theres'ulfithat it has takena considerable period of time-to open or closethem. I Among the objectsof this invention are to providea gate which can be opened and closedfaster than'heretoiore'; to provide such agate and appurtenant partswhich are simple inconstruct'ion and: easy to operate, and to providemeans for easily and quickl'y opening and closingit. v

S uch objects are" accomplished by having the gate" move vertically, upto closed position, and down'toopen positionf'into a chamber below thedocltni'outh; and another object of the invention isto prevent too greatan accumulation of siltfor debris injsuch chamber.

Further objects of this' inven'tion are to provide. meanswhich'operateat the end of the closing movement of r the gate to improvethe sealing efiect, and also to provide means which break's the" seal atthe beginning of the opening movement;

Still further object's'of this invention are todecrease the: gravityefiect'of the actualma's's of the gate, tovariably" control such gravityeffect to causetlie gate to ascend, desce'ndor 'rei'nai1'1stationar'yi-and to provide asafety means to retain the gate in'itsupper onclosed'position.

Additional objects of the invention will heap parent on readingspecification.

The above" objects are attained by application of' novelprincip'lesantifby' novel structural features of theg'ate and appurtenant parts, aswill appear more detailxli'reina' ft'er. The pre fe'rredexemplific'at'ion of the invention is illus'? determine accompanyingdravvings, on'which' vFi mouthof the 'basin in section, with the gate inupperor closed position;

Fig.2is'a section on the line 22 on. Fig. 1; Fig. 3' is an enlargementof a part of Fig. 1, showing more details;

Figs. 5, 6 and "1 are sections on the'lin'es 4-4', 5' 5, 6 '6"an'd 1 1respectively, on Fig. 3';

Fig-8 is a detail viewishowing a holding pin in lilafi iiifid' aDpuf-i'i t-l'naI'll;"limi -11S in 1101120111331 Sdtibl'ff Fig. 9 is asectibnon the l'ine 9-9 on Fig. 8; Fig. 10 is a top pla'ri view of thegate and basin mouth; Fig. 11 is a'section of the 'gate on the'line I[-11 on Fig. 10;" I

Fig.- 12 isfifs'ctidn Oh the lifie' 12-4 2 OIIFig 11;. Fig. 1 3' is as'ec'tifin o th l-iifie' I3l3 0n Fig. 1; Fig. 14 is n enlarged verticalcross section through the gate and ate chamber; -s'1'i0'W'ifig' the gatein its' lower, c1osedpositionj I Fig. 'l5"is a-'s"dti the'liniFE-lfi onFig. 14'; Fig. 16 is a'i'sectib'n'onth l'in'e iii-Won 1'4; Fig. 17 is anenlarged section' of a detail: and Fig; 18i's' a schematic vieweta-"double act'ing hydraulic cylinder. I

k The preferred features of the invention fol-' low. The gateisiboglike' and hollow, beingm'a' de of plates'yof stee'lor of any othersuitable mat'eriaL-wit'h any 's'uitabl'e type of bracing that may bedesired ftjrioyes"-prin eipally vertically, from its uppermofstjor"fully closed position into-a chairi her in which it assumes ,its'ilowermost or fully; open position; and *vice ve'rs'a. It also undergoestransverse movements-at the end" of its closing and-at ;the begfii ningof its opening movement's, t1ie f0flfl'i6i {brine purpose off rnaking' aseal, and thelatter'ior the' purpose-of breaking the sea-1, so that thesealing material will'n'ot be abraded or tornby the movement of thegate. Passages are providedin the te to allow watertofiow through it" ait"le' r enters the chamber.

Thegate' s provided itiithibne' ormore buoyancy'chambers'which is orarelocated tobalance the gateand arei below the, lowest water level;

for the'pu 'se of decreasing the weight eithegate. It is alsoprovidedwith-'o'neorrnore ballast chambers with riieans to" run waterthereintol and'means preferably of tn jompr s ed air, typefto'ievacuatesuch water. The buoyancy and ba'l astsrsi be s qr e at t t r; ejfi' ct's,bman e; each other so; that the gate will float stationary w en the'balla'st -chamber or chambers are fiI1ed to a predetermiiiedde'gref' antif se' wfith ess ball v t water pr sent; makin -1 cor'itr'ol of the"movement of the gate easy" and and will sink with more Sensitive to theamount of ballast water present so that the gate will move up or down asfast as desired. Springs resiliently terminate the upward and downwardmovements of the gate. In its lowermost position the gate rests onsuitable supports at the bottom of the gate chamber; and it is held bysafety means in its uppermost position. Means are provided to prevent anaccumulation of silt or sediment at the bottom and mouth of the gatechamber. Although the gate has preferably all of these features, yet oneor more may be omitted as occasion may make expedient. Referring now tothe drawings for a detailed description, the gate 21 (Figs. 1, 2, 10, 11and 12) which selectively closes and opens the mouth of the gravingclock 22 moves downwardly into the gate chamber 23, Fig. 2, formed by acasing 24 preferably made of concrete and integral with the dock bottom26 and dock opening sill 21. When open,

the gate permits a ship to float into or out of theydock, and whenclosed, it seals off the opening to permit evacuation of the waterwithin the dock. The gate has a pluralityof hollow, boxlike subdivisions28 (Fig. 11) some of which have openings 29 to permit water to passthrough the gate as it is raised or lowered. Some of these subdivisions,as those designated 3| can be sealed off completely by suitable means toprovide buoyancy chambers which lend buoyancy to the gate and thus makeit lighter. Access to such chamber is provided by manholes 32 with acover 33 to seal them, the covers being held in sealing position by aclamp 34 and a bolt 35 passing through a threaded opening in the clampand pressing upon the cover. There may be one or more of such buoyancychambers, any number of them that may be found expedient; and it ispreferred that they so balance the effective Weight of the gate thatthere is no tendency for any part of the gate to rise or sink fasterthan another. Such chamber or chambers are to be sealed during theconstruction, installation or repair of the gate, before they aresubmerged.

One or more of the subdivisions of the gate, as for example thatdesignated 36, has (or have) means to hold a controllably variableamount of ballast water, to provide a ballast chamber. The ballastchamber or chambers, similarly to the buoyancy chambers, is or arelocated so that no part of the gate has a greater tendency than anotherto rise or sink. Each ballast chamber 36 has a normally closed, inwardlyopening valve 31 (Fig. 11) and a normally closed, outwardly openingvalve 38, the former being preferably but not necessarily at the top andthe latter at the bottom for a purpose which will appear hereinafter.The valve 38 is normally held closed by a spring 39, aided by the waterpressure on the outer face of the valve. A vertical push rod 41 is of alength to loosely contact both the lower face of the valve 31 and theupper face of the valve 38. Brackets 42, through which the rod canslide, maintain it in proper position. A hydraulic cylinder 43, shownenlarged on Fig. 18, is carried by the gate, its piston rod 44 normallyresting loosely on the upper face of the valve 31. Pipes 46 and 41 leadinto the cylinder at one end, thereof, that is at one side of the piston41a and pipes 48 and 49 at the other. Valves 51, 52, 53 and 54 controlflow through each of these pipes respectively. Pipes 46 and 48 are eachconnected to a source of water under pressure (not shown), and pipes 41and 49 are exhaust or waste pipes. A pipe 56 controlled by a valve 51 isconnected to the ballast chamber 36 and to a source (not shown) ofcompressed air. All of the valves 51, 52, 53, 54 and 51 are located forconvenient operation. The piston 41 at which carries the rod 44 can bemoved selectively down or up by means of the valves 5|, 52, 53 and 54.With the valves 51 and 54 open and the valves 52, 53 and 51 closed, thehydraulic pressure will move the piston down, the piston rod 44 thenopening the valve 31 as shown in dotted lines. This moves the push rod4| down-to open the valve 38 against the pressure of the spring 38, asshown in dotted lines. With the valves 51, 54 and 51 closed and thevalves 52 and 53 open, the piston and its rod will be moved upwardly bythe hydraulic pressure, permitting the spring 39 to close the valve 38,which closes the valve 31 by means of the rod 4|. The gate is lowered byadmitting suflicient water into the ballast chamber or compartment 36,which is accomplished by opening the valves 31 and 38, air within thecompartment then escaping therefrom through the open valve 31 whilewater enters through the open valve 38 and perhaps also through the openvalve 31. The gate. is raised by removing sufiicient water from thecompartment 36, Which is accomplished by opening the compressed airvalve 51. The air is under suificient pressure to open the valve 38 andforce water present out therethrough. The push rod 41 then does notmaintain the valve 31 closed, but the air pressure in the ballastcompartment does. By properly designing the gate featuresafiording'buoyancy, and the ballast feature, with respect to each otherand to the weight of the gate, any practical maximum speed of ascent anddescent of the gate is attainable and such speeds of ascent and descentare easily variably controllable to any not greater than such maxima.

Projecting upwardly from the end walls of the casing 24 which receivesthe'gate when open, are walls 61 (Figs. 1, 6 and 7) which are preferablyof concrete and may be integral with such end walls. Such walls 6|preferably have flanges 62 to form opposite U-shaped members whichtogether form a passageway within which the gate moves. The gate itselfhasa tapered cross section, being narrower at its sea side than at itsdock side. Attached to its oblique ends are upperguide shoes 63 andlower guide shoes 64, by means of brackets 66 and 61 respectively. Guiderails 68 are attached to the walls 61 the guide shoes sliding along suchrails as the gate ascends or descends. The major part of eachguide rail68 is straight and vertical so that most of the movement of the gate inopening and closing is vertical. 7 There are however two jogs 69, 16

in each guide rail, one for the upper guide shoe and one for the lower,which cause the gate to move a short distance toward the dock side atthe end of its closing movement and in the reverse direction at thebeginning of its opening movement. Vertical portions 11 (Figs. 6 and 7)of a U-shaped sealing striplie between the end-v wise parts ,of the dockside face of the gate and the adjacent faces of the dockside flanges 62when the gate is up, these vertical portions being connected by aportion '12 (Fig. 2) extending across between the lower part of the dockside face of the gate and the, dock side sill 13. The sealing stripmaybe attached to either one of the members between which it is compressed,although it is often preferred to attach it to the gate. It extendsupwardly (as at 11) to a point above the highestwater level, andispreferably made of rubber or equivalent flexible waterproof material.It preferablyhas a cross section simi- ,-.over the shelf I01.

'"Blocks'I'OIi (Figs. 1, 13,

l'arto'that of a lamb chop, having aflatpor-tion 16 fo'r attachmentpurposes and an enlarged rounded portion'TI for sealing purposes.Ilan1ps 18 held by bolts I9 and nuts 80 aifix the sealing strip, forexample to the gate. It is nowapparent that a water-tight seal is madebetween the gate and the structure forming themouth of the-dock basin bythe movement of the gate at the end of its closing movement toward suchstructure; and similarly the gate moves away from such structure at thebeginning of its opening movement to free the sealing material tominimize abrasion and tearing thereof.

The upper face of the bottom of the gate chamber is formed to have aseries of bowl-like lconcavities or depressions 81 (Figs. '1, '2, 13, 14and 16) extending across the width thereof, with the depressions closelyadjacent each other and adjacent ones having common defining walls 82.Alpipe or conduit 83 is embedded or formed in such bottom, which has across section which increases from a smaller closed end 84 to. thelarger open end 86, the latter being the outlet end. The gate chamberbottom has perforations 81 at the lowermost points of the depressions8I, and the pipe 83 has perforations 88 connecting therewith. The end.86 of the pipe '83 opens into a well 89 in which is a pump 9I whichpumps water within and flowing into the bottom .of the well 89 upwardlythrough a pipe 92 having an outlet 93 at the sea side of the gate andappurtenant .parts or at some remote point. This produces suction at theopenings .81. Means such as a motor 94 is provided to drive the pump.Thus sediment and small debris which can build up a pile or cake withinthegate chamber 23 will flow out with water removed by the pump 9|.Water will flow into the gate chamber from the sea as the pump isoperated. Pipes 96 supply water under pressure to jets 91 whichpreferably have flared elongated outlets. These jets are arranged at oradjacent the bottom of the gate chamber, they are so orientated withrespect to each other as toproduce a heavy swirl of water in eachdepression BI, and they can be used to break up any cake that may haveformed and to aid in flushing out the bottom of the gate chamber. Ariser 9,8 is connected to a suitable source of water under pressure andto the pipes 96. In the case of very large gates, the pump 9! may have acapacity of the order .oftwelve thousand (12,000) gallons per minute,and, the pipes 95 may have a diameter of the order of three (3') inches.

The gate sometimes remains closed for long periods of time, and meanscan be provided, if desired, to then prevent ingress of silt and debrisinto the gate chamber to lessen the necessity for frequent flushingthereof if conditions would otherwise require it. Such means maycomprise aflat shelf II'II (Figs. 2 and 17) of steel or other suitablematerial attached to, and projecting from the face of, the gate, and athick somewhat flexible sheet I 02 of rubber or equivalent mae terialattached to the gate sill and projecting The parts IOI and-I02 are solocated that they contact to form a self-sealing means as the gate isclosed to decrease. very substantially any ingress of silt or othersolids into the gate chamber. A pipe I03 (Fig. 2) to which a series ofnozzles l04 is connected with the nozzles directed toward the parts IOIand 1.02, can be used to project water, and thereby break up and removeany deposit, at the parts I04. and I02. 7 v c I 14 and 16) of wood orother :suitable materiaLrestonsQme of the high partsr82 of the bottom ofthegate chamber which may-have fiat tops for this purpose, and are fixedin position .by attachment to the concrete by bolts 101. The blocksextend cross wise, in the direction between sea side and basin side, andthe gate'rests upon them when in its lowermost 11051.- .tion, but itsweight thereon is controllable to .a minimal. amount by controlling thebuoyancy of the gate. The blocks are spaced apart from each other andneed be but' few in number. Softening of. the .blow of the gate as itdescends, upon the blocks, even though. it descends comparatively fast,can be accomplished by means of springs 108 located at both ends ofblocks which are between the center of the bottom of the gate chamberand each end thereof. Vertical movable cyli-ndrical casings I09 of whichthe top ends are closed and the bottom ends are open, rest upon thesprings, and prevent ingress of sediment'and debris to the spring. Thesprings rest upon depressed abutments III formed in. :the chamberbottom, surrounding which are annular passages M2 to permit axialmovement .of the casings I09. The tops of the casings I09 are normallyabove the tops of the cross blocks, to receive and lessen the impact ofthe descending gate. Truncated-conical aprons .3 of rubber-or thexlike,attached suitablyto the bottom by .annur- Iar plates H4 held in place bybolts H6, contact the casing I09 as they move up and down and preventingress .of silt and. debris.

The gate is also stopped resiliently at therend of its upward movementby means shown on Figs. 1 and 3'. Brackets lI'I .are attached to thegate and cups [I18 are attached. to the brackets, as. by bolts H9.Coiled springs PM are suitably attached to the cups with their lowerends inthe bottoms thereof, the upper ends of the springs zheingfree.Brackets I 22 are attached, as by bolts I23, to convenient parts of eachwall .6I, such brackets projecting over the springs I2 I. It is nowapparent that the springs II9 strike against the brackets I22 as thegate rises, so that its :upward movement is resiliently stopped. I

'Thegate (Figs. 1, 11 and 12) has valve-con!- trolled passages I26therethroughto permit water to flow from the sea to the dock basin, whenwork on a ship in the basin has been completed and it is desired tofloat the ship out. Valves I21 which control them comprise plate-likegate valve members I28 which are moved by-hydraulic cylinders I29 havingappurtenant parts similar to those illustrated on Fig. 18 and operatingsimi-.-

direction by hydraulic cylinders I36 having appurtenant parts like, andoperating similarly to, those illustrated on Fig. 18. Members I31adapted to receive the pins are-attached to the gate and have verticallyelongated grooves or openings I38 into which the pins can extend. Thehydraulic cylinders are operated to extend the pins'when the gatehasreached its'uppermost position. The elongated grooves I33 are so,posi- 'tioned that the tops thereof are slightly above the pins I 33 topermit easy entrance of the pins there into. The gate can then beallowed to. remain there or to descend the very short distance 118095.-sary to make the tops of the grooves contact the pins. There need not bemuch weight onthe pins, due to the controllable buoyancy of the gate.Once the gate has been closed, the waterin the dock basin can beevacuated by suitable means, conventional or otherwise; and theincreasing pressure of the water on the sea side of the gate holds ittightly closed. When the dock basin has again been filled with water,the hydraulic cylinders I36 are operated to withdraw the pins I33,raising the gate slightly first if this is necessary,

and the gate can then be opened by admitting A water to the ballastchamber.

Means can be provided to raise and support the gate for servicing orrepairing it while a caisson gate (not shown) is used to prevent accessof water thereto. The supporting means (Figs. 1, 2, 3, and 4) comprisescrane carriages I4I .over each end of the gate and mounted to be movedin either direction between the sea side and the dock basin side. Withthis in view, girders I42 are supported on structural members I43 toform a, bridge over them and over each end of the gate. Rails I44 areafiixed to the girders and the carriages are mounted on flanged wheelsI46 which ride on the rails. Threaded bars I41 are .suspended from thecarriages by means of nuts, I48, they can extend through openings inattachment members I49, withdrawal from which can be prevented by nutsII. The members I49 can be permanently or removably attached to the gateby conventional means. The carriages I4I'oan be rolled to the properpositions, the bars I41 inserted through the attachment members I49which may be attached to the gate at both ends thereof, and the gate canthen be raised to any convenient height by turning the nuts I48 in theproper direction. Certain details have been illustrated and describedfor the purpose of explaining the invention without limiting it, and maybe changed or omitted without departing from the spirit of theinvention, the scope of which is set forth in the appended claims.

What is claimed is: 1; A graving dock having walls forming a mouth for aship to pass through, a vertically movable gate to close and open saidmouth, sealing means between said walls and said gate, shoes on saidgate, guide rails on which said shoes ride to guide the verticalmovement of said gate while preventing said sealing means from making aseal between said walls and said gate,

said guide rails having jogs therein to guide the gate to cause saidsealing means to make a seal between said walls and said gate at the endof .the closing movement of said gate and to open for raising andlowering said gate including curved guide members attached to said walland cooperating with projections on the edges of said 'gate for movingsaid gate laterally so as to bring said sealing strips into engagementwith said tion, and means to support, said gate in open position withits bottom above the bottom of said chamber comprising a series ofhorizontally disposed blocks at the bottom of said chamber which projectthereabove and a series of resilient members adjacent to andprojectinabove said blocks to thereby cushion the impact of said gate as it comesto rest on said blocks.

3. A graving dock having walls forming a mouth for a ship to passthrough, a, vertically movable. gate to close said mouth, a casingforming a chamber, to receive said gate under said mouth, said gatebeing opened by lowering it into said chamber and closed by raising itabove the water level sealin strips on said gate, means for raising andlowering said gate including curved guide members attached to said wallsand cooperating with projection on the edges of said gate for movingsaid gate laterally so as to bring said sealing strips into engagementwith said walls when said gate is raised to a closed position, andresilient means to limit the upward movement of said gate comprisingbrackets attached to said gate having spring means mounted thereon andbracket projecting from the walls of the chamber and so positioned thatboth brackets resiliently engage each other and restrict the upwardmovement of said gate as it rises to the closed position.

4. A graving dock having walls forming a mouth for a ship to passthrough, a vertically movable gate to close said mouth, a casing forminga chamber to receive said gate under said mouth, said gate being openedby lowering it into said chamber and closed by raising it above thewater level sealin strips on said gate, means for raising and loweringsaid gate including curved guide members attached to said walls andcooperating with projections on the edges of said gate for moving saidgate laterally so as to bring said sealing strips into engagement withsaid Walls when said gate is raised to a closed position, and means toremove water and sediment from the bottom of said chamber comprisinglaterally disposed spray pipes adapted to project water over the bottomof said chamber insuch manner as to dislodge deposits of sediment and apump means adapted to discharge the water and sediment from the chamber.

5. A graving dock gate comprising walls forming a ballast chamber havingfirst and second openings a first valve member at said first opening andoperable by pressure from without said chamber, a second valve member atsaid second opening and openable by pressure from within said chamber,said members being openable by movement in the same direction, means toconnect said chamber with a source of compressed air, a valve in saidconnecting means, means to exert pressure from without said chamber onsaid first member means to maintain said second member normally closed,means to cause said second member to open with said first member andsaid first member to close with said second member, said second memberbeing openable independently of said first member, said first memberbeing closable independently of said second member.

6. In a graving dock having walls and a mouth for ships to pass through,the combination of a vertically movable gate, means for alternatelymoving said gate upward to close and downward to open said mouth,sealing members rigidly fastened to the bottom and side edges of saidwalls, when said gate is raised to a closed po'si gate and adapted tocontact the mouth portion of said dock when said gate has been elevatedto close said mouth, and curved guide means located along and fastenedto the side edges of said mouth and cooperating with projection on theside edges of said gate for moving said gate laterally to bring saidsealing members into engagement with the mouth of said dock upon theelevation of the said gate.

'7. In a graving dock having walls forming a mouth for ships to passthrough, the combination of a vertically movable gate, sealing stripsrigidly fastened. to the bottom and side edges of said gate and adaptedto contact the walls of said mouth, when the gate has been elevated toclose said mouth, and means for alternately moving said gate upward toclose said mouth and downward to open said mouth including curved guideelements fastened to the walls of said mouth and cooperating withprojections on the side edges of said gate for moving said gatelaterally to bring the sealin strips on said gate into complete contactwith the walls of said mouth when said gate is elevated, and forisengaging said sealing strips from the walls of said mouth when saidgate is lowered.

8. In a graving dock having a bottom and walls forming a mouth for shipsto pass through the combination of a vertically movable gate, means foralternately moving said gate upward to close and downward to open saidmouth, a casing forming a chamber below said mouth and adapted toreceive said gate, when it is lowered, a plurality of flanges projectinginwardly from each side wall of the dock mouth so as to provide verticalchannels adapted to receive the opposing side edges of the gate therein,sealing strips rigidly secured to the side edges of said gate andadapted to contact the flanges on said walls, a separate sealing stripsecured to the bottom portion of said gate and adapted to contact thebottom of said dock when said gate is elevated and curved guide meanslocated within the channel on the said walls and cooperating withprojections on the said edges of the gate for moving the gate laterallyto bring the said ber and closed by raising it about the water level,

sealing members fastened to the side and bottom edges of said ate andadapted to engage the bottom and walls of said dock so as tocontinuously encompass thermouth of said dock up to the water level whensaid gate is in a raised 5:

position, means for alternately raising and lowering said gate includingcurved guide means secured to the walls of said mouth and cooperat- 10ing with projections on the side edges of said gate for alternatelycausing said sealin members to become engaged with and disengaged fromthe mouth of said dock, when said gate is raised and lowered and meansfor positively locking said gate while in a raised position.

10. A closure for graving docks and like comprising a compartmented gateadapted for vertical movement and to serve as a closure when in itsupward position, U-shaped vertically extending channels located oppositeeach other at the entrance to the graving dock and extending below thebed of the dock a distance equal to at least the height of compartmentedgate to thereby form a gate chamber, sealing strips rigidly fixed to theside edges and bottom of said gate, vertically extending rails having aplurality of jogs therein fixed to the base wall of each channel andadapted to cooperate with projections on the sides of said gate whensaid gate is raised, so as to move the gate laterally and bring thesealing strips on the side edges of said gate into engagement with theinner portions of said U-shaped channels.

11. In a graving dock having walls and a mouth for ships to pass throughthe combination of a vertically movable gate, means for alternatelymoving said gate upward to close and downwardly to open said mouth,resilient sealing members rigidly fastened to the bottom and side edgesof said gate and adapted to contact the mouth portion of said clock,when said gate has been elevated to close said mouth, curved guide meanslocated on the side edges of said mouth and cooperating with projectionson the side edges of said gate for moving said gate laterally to bringsaid sealing members into engagement with the mouth of said dock uponthe elevation of the said gate, a casing forming a chamber to receivesaid gate under said mouth when said gate is lowered, means for removingwater and sediment from the bottom of said chamber comprising spraypipes laterally disposed in the bottom of said chamber and in such amanner as to dislodge deposits of sediment and a pump means adapted todischarge the water and sediment from the chamber, and means forpositively locking said gate while in an elevated position.

EINAR T. LARSEN.

REFERENCES CITED The-following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,530,394 Muller Mar. 17, 19251,618,545 Mann Feb. 22, 1927 FOREIGN PATENTS Number Country Date 25,970Great Britain 1901

